Space operations such as rendezvous, docking, and proximity operations can be very challenging and are complicated by the precise nature and errors of the measurements for navigating and controlling the relative motion and orbits between the spacecrafts or other space targets of interest. These operations are generally performed using a suite of sensors which provide navigation data. The typical sensor suite may include various types of instruments which provide measurements from the component systems, such as visible and infrared sensors, laser range finders, LIDARs (light detection and ranging), LADARs (laser detection and ranging), inertial measurement units, and GPS (global positioning system) receivers.
In connection with docking missions, systems have been developed that provide range measurements from laser range finders, or that use data from visual cameras. The laser ranger finders are used to measure ranges, while the visible wavelength cameras measure relative angles, and inter-distances based on that information.
Imaging LADAR systems can be used in connection with the identification of target objects or regions of a body. LADAR systems have also been recognized as being useful in various landing and/or docking scenarios. For example, the use of LADAR systems for docking spacecraft has been proposed. LADAR systems have also been proposed for use in connection with landing vehicles onto surfaces.
For meeting the needs of these missions, three-dimensional imaging sensors, particularly Laser Detection and Ranging sensors, have emerged as a leading candidate for a variety of reasons. Docking systems have used visual cameras as a sole source of navigation data, but these sensors aren'table to directly measure the range between the sensor and the target. Other docking systems have used scanning LADARs, but these sensors are higher in mass, require more power and are less reliable than a flash LADAR sensor. For some landing systems, present LADAR solutions typically involve two LADAR sensors. One of the LADAR sensors uses the complex coherent LADAR technique to provide ranging, descent and lateral velocity information while the other LADAR provides terrain aided navigation and hazard detection and avoidance (HDA) using a flash three-dimensional LADAR. However, the use of multiple sensors increases the mass and power requirements, reduces reliability and adds complexity to the landing function.
In order to perform real world docking or landing procedures, a target object or area in the field of view of the LADAR must first be identified. The identification of a target using a LADAR system typically involves iterative processes. For example, previously developed algorithms, such as the RANdom SAmple Consensus (RANSAC) or natural feature image recognition (NFIR) algorithms are significantly slower in the identification process, and require the use of iterative methods to arrive at a solution. As a result, such processes are relatively time consuming, and usually involve some degree of uncertainty.